I have had a kind of low to medium pitch whine in my rear axle at speeds of 40-45 and 77-85. The higher speed could be heard over the radio playing at a comfortable level. I read on some of the older posts that this could be an inherent problem and I even had a dealer (not the one I bought the truck from) say that is the way the 9.75 rear axle is (that is from the tech and shop foreman's mouth). I took it to the dealer I bought the truck from and the tech immediately knew the gears were mis-aligned and is replacing the gears, bearings and everything else because the truck only has 2000 miles on it. I hope to pick the truck up this afternoon, after work, and I will ask to talk to the tech and see if he will tell me exactly what was wrong so I could post the information here for other owners who have noisy axles.
BTW,The noise bothered me more after I drove my buddy's 03 HD and it was quiet no matter how fast you went as well as my Dad's 01 with the same drivetrain, that is why it is in the shop getting fixed. I also let the service guy know I drove another '03 truck and did NOT hear the noise. I think it helps to force their hand at fixing it. That's my experieince so far, I will post more info later today. It was also depressing seeing her on the lift getting her A** fixed like that, plus I had to drive the wife's focus into work today, it needs four more cylinder's (a 302 perhaps, I don't think she would mind too much) javascript:smilie('')
Brian

 

Got my truck back and it is less of a noise but still a little there. They said I could bring it back if I am not happy. I may be back to discuss options. The tech said that the backlash was set too tight and that the noise was more than unacceptable before it was fixed. The tech was also amazed (actually disbelief fits his reaction) that the other dealer just pawned it off. I guess if nothing works,it may be time for an exhaust system to drown out the noise.
Brian

 

What ratio do you have?

 

What ratio do you have?

It is my understanding that "silent gears" of a ratio 3.73 and higher is the exception rather than the rule.

My original 3.55's were slightly noisy and I took it back to my dealer on three seperate occasions. They replaced the pinion bearings one time and everything except the LS carrier on another. Thet even replaced the wheel bearings out of desperation.

I have come to accept the slight noise as they are now 4.10's.

 

It is a 3.55 LS with a 9.75 axle. At least the tech told me he would replace the whole rear-end for me if I was not happy with the results. After driving around yesterday night, the noise at 40-45 is less, but the 75-85 is a lot less. In that upper range, it probably reduced the noise by about 50 percent. I will take it back to se if we can get more of the noise out of it. Maybe, I will see if the tech will slip in some 3:73's if I have to leave it in there with this noise. I might as well get some performance out of it.

 

I have the same problem, my truck was built in aug 2001, and I noticed it since 11/01. I have 18k on it now and will take it to the dealer for checking along with your posts. I dont have the posi rear-end, did you? My problem is really straight out, at 45mph and at 80mph, on the dial!

 

The local Ford dealer rebuilt the differential twice on my '01 Screw due to an annoying whine at 40-50mph, once at 12k and once at 34k, but the whine remained. Finally, with 35.8k miles, Ford engineering conceded that there was probably a casting flaw in the housing such that the pinion depth could never be properly set, and authorized the dealer to replace the entire rear axle assembly, guts and all, less the axle shafts and brakes. This seems to have licked the problem (knock on wood with crossed fingers). Must give my compliments to the service advisor for persevering and seeming to work for me instead of against me, as so many seem to do.

If the possibility of a miscast housing has not already been discussed, you might want to bring it up with the service people.

 

SM : Did you post about your experiences getting the rear end whine eliminated atleast several months ago ? I remember a similar post from an owner then. I had my rear end gears and bearings replaced twice at 2 different dealers and the 45 mph whine remained. I have about 6,000 + and/or 6 mos. left on warranty. I have moved to NM from East Coast and will go to best Abq Ford service dept soon and tell them about how Ford engineers admitted some housings were defective and that it causes whine from misalignment of rear gears. I believe that owner was from Texas. My truck is an 02 supercab,5.4 L, 3.55 standard rear. (bought in 9-01)

 

znstr,

Yes, I posted essentially the same information several months ago. Seemed like there was a chance it could be useful in this situation. I am in Louisiana, however, not Texas. My truck is an '01 Supercrew bought in Aug 2000. I have 3.55LS.

SM